Electroluminescent device

ABSTRACT

An electroluminescent device which has an electroluminescent layer formed of a binuclear, trinuclear or polynuclear rare earth organic complex in which the metals are linked through a bridging ligand.

The present invention relates to electroluminescent devicesincorporating electroluminescent materials.

Materials which emit light when an electric current is passed throughthem are well known and used in a wide range of display applications.Liquid crystal devices and devices which are based on inorganicsemiconductor systems are widely used, however these suffer from thedisadvantages of high energy consumption, high cost of manufacture, lowquantum efficiency and the inability to make flat panel displays.

Organic polymers have been proposed as useful in electroluminescentdevices, but it is not possible to obtain pure colours, they areexpensive to make and have a relatively low efficiency.

Another compound which has been proposed is aluminium quinolate, butthis requires dopants to be used to obtain a range of colours and has arelatively low efficiency.

Patent application WO98/58037 describes a range of lanthanide complexeswhich can be used in electroluminescent devices which have improvedproperties and give better results. Patent Applications PCT/GB98/01773,PCT/GB99/03619, PCT/GB99/04030, PCT/GB99/04024, PCT/GB99/04028,PCT/GB00/00268 describe electroluminescent complexes, structures anddevices using rare earth chelates.

We have now devised electroluminescent devices incorporating otherorganometallic electroluminescent materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2 a-2 b and 3 show ligands for bridging the metal atoms in theelectroluminescent materials of this invention.

FIGS. 4 a-4 l show additional ligands for bridging the metal atoms inthe electroluminescent materials of this invention.

FIGS. 5 a-5 f, 6 a-6 e, 7 a-7 f and 8 a-8 h show further ligands forbridging the metal atoms in the electroluminescent materials of thisinvention.

FIGS. 9 and 10 show electron transporting compounds used in theelectroluminescent devices of this invention.

FIGS. 11, 12 a-12 d, 13 a-13 c, 14 a-14 d, 15 a-15 b, and 16 a-16 c showhole transporting materials used in the electroluminescent devices ofthis invention.

FIG. 17 shows additional bridging ligands for bridging the metal atomsin the electroluminescent materials of this invention.

FIG. 18 shows binuclear complexes useful as electroluminescent compoundsin accordance with this invention.

FIGS. 19 a-19 c show generic formulae of further binuclear andtri-nuclear complexes which are useful as electroluminescent compoundsin accordance with this invention, these complexes illustrating the rareearth chelate bis-phosphate oxide complexes, rare earth chelatetris-phosphine oxide complexes and rare earth chelate bisphosphinimino-phosphane oxide complexes which are within the scope ofthis invention.

FIG. 20 shows the formulae of some binuclear and tri-nuclear compoundsof terbium and europium which are useful as electroluminescent compoundsin accordance with this invention.

FIG. 21 is a diagram of an OLED in accordance with this invention.

FIGS. 22 and 23 are graphs of current efficiency against voltage (FIG.22) and brightness against voltage (FIG. 23) for an electroluminescentdevice as described in Example 19.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to the invention there is provided an electroluminescentdevice which comprises sequentially a first electrode, a layer of anelectroluminescent compound and second electrode in which theelectroluminescent compound is selected from binuclear, trinuclear andpolynuclear complexes of rare earth metals.

By binuclear is meant that there are least two metal atoms in thecomplex, at least one of which is a rare earth metal the other metalscan be a rare earth or non rare earth metal one in which the metals arelinked by a bridging ligand i.e. of formula

where M₁ is a rare earth metal and M₂ is a rare earth or non rare earthmetal Lm and Ln are the same or different organic ligands, x is thevalence state of Lm and y is the valence state of Ln and L is a bridgingligand. For example x will be 3 when M₁ is in the III valence state andy will be 2 when M₂ and is in the 2 valence state etc.

By trinuclear is meant there are three metals joined by a bridgingligand one of which metals is a rare earth metal and at least one ofwhich is a non rare earth metal i.e. of formula

where L is a bridging ligand and at least one of M₁, M₂ and M₃ is a rareearth metal and the other metals can be a rare earth or non rare earthmetals. Lm, Ln and Lp are organic ligands and x is the valence state ofM₁, y is the valence state of M₂ and z is the valence state of M₃

By polynuclear is meant there are more than three metals joined bybridging ligands and at least one of the metals is a rare earth metaland the other metals can be a rare earth or non rare earth metal.

Preferably the rare earth metal is a metal having an unfilled innershell and the preferred metals are selected from Sm(III), Eu(II),Eu(III), Tb(III), Dy(III), Yb(III), Lu(III), Gd (III), Gd(III) U(III),Tm(III), Ce (III), Pr(III), Nd(III), Pm(III), Dy(III), Ho(III), Er(III),Yb(III) and more preferably Eu(III), Tb(III), Dy(III), Gd (III).

The non rare earth metal can be any non rare earth metal e.g. lithium,sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium,strontium, barium, copper, silver, gold, zinc, cadmium, boron,aluminium, gallium, indium, germanium, tin, antimony, lead, and metalsof the fist, second and third groups of transition metals e.g.manganese, iron, ruthenium, osmium, cobalt, nickel, palladium, platinum,cadmium, chromium, titanium, vanadium, zirconium, tantalum, molybdenum,rhodium, iridium, titanium, niobium, scandium, yttrium etc.

For example (L₁)(L₂)(L₃)(L . . . )M₁-L-M₂(L₁)(L₂)(L₃)(L . . . ) where(L₁)(L₂)(L₃)(L . . . ) are the same or different organic complexes.

For example x will be 3 when M₁ is in the III valence state and y willbe 2 when M₂ and is in the 2 valence sate.

The bridging ligands L are preferably bidentate or tridentate ligandsand are preferably bis or tris phosphane oxide complexes e.g. of formula

where the groups R which can be the same or different are selected fromhydrogen, and substituted and unsubstituted hydrocarbyl groups such assubstituted and unsubstituted aliphatic groups, substituted andunsubstituted aromatic, heterocyclic and polycyclic ring structures,fluorocarbons such as trifluoryl methyl groups, halogens such asfluorine or thiophenyl groups, n is preferably 1 to 10 e.g. 1 to 5 or asshown in FIG. 17 of the drawings in which Ar are the same or differentunsubstituted or substituted aromatic groups.

Or bis(diphenylphosphinimino-phosphane oxides e.g. of formula

where R and n are as above. Preferably the groups R are unsubstituted orsubstituted aromatic groups or as shown in FIG. 17.

Examples of other ligands are also shown in FIG. 17 of the drawings

The groups Lm, Ln, Lp etc. which can also be the bridging ligands mayall be the same or different and can be selected from β diketones suchas those of formulae

where R₁, R₂ and R₃ can be the same or different and are selected fromhydrogen, and substituted and unsubstituted hydrocarbyl groups such assubstituted and unsubstituted aliphatic groups, substituted andunsubstituted aromatic, heterocyclic and polycyclic ring structures,fluorocarbons such as trifluoryl methyl groups, halogens such asfluorine or thiophenyl groups; R₁, R₂ and R₃ can also form substitutedand unsubstituted fused aromatic, heterocyclic and polycyclic ringstructures and can be copolymerisable with a monomer e.g. styrene. X isSe, S or O, Y can be hydrogen, substituted or unsubstituted hydrocarbylgroups, such as substituted and unsubstituted aromatic, heterocyclic andpolycyclic ring structures, fluorine, fluorocarbons such as trifluorylmethyl groups, halogens such as fluorine or thiophenyl groups ornitrile.

Examples of R₁ and/or R₂ and/or R₃ include aliphatic, aromatic andheterocyclic alkoxy, aryloxy and carboxy groups, substituted andsubstituted phenyl, fluorophenyl, biphenyl, phenanthrene, anthracene,naphthyl and fluorene groups alkyl groups such as t-butyl heterocyclicgroups such as carbazole.

R₁, R₂ and R₃ can also be

where X is O, S, Se or NH.

A preferred moiety R₁ is trifluoromethyl CF₃ and examples of suchdiketones are, banzoyltrifluoroacetone, p-chlorobenzoyltrifluoroacetone,p-bromotrifluoroacetone, p-phenyltrifluoroacetone,1-naphthoyltrifluoroacetone, 2-naphthoyltrifluoroacetone,2-phenathoyltrifluoroacetone, 3-phenanthoyltrifluoroacetone,9-anthroyltrifluoroacetonetrifluoroacetone, cinnamoyltrifluoroacetone,and 2-thenoyltrifluoroacetone.

The different groups Lm, Ln and Lp may be the same or different ligandsof formulae

where X is O, S, or Se and R₁ R₂ and R₃ are as above

The different groups Lm, Ln and Lp may be the same or differentquinolate derivatives such as

where R is hydrocarbyl, aliphatic, aromatic or heterocyclic carboxy,aryloxy, hydroxy or alkoxy e.g. the 8 hydroxy quinolate derivatives or

where R is as above or H or F or

The different groups Lm, Ln and Lp may also be the same or differentcarboxylate groups

where R₅ is a substituted or unsubstituted aromatic, polycyclic orheterocyclic ring a polypyridyl group, R₅ can also be a 2-ethyl hexylgroup so Ln is 2-ethylhexanoate or R₅ can be a chair structure so thatLn is 2-acetyl cyclohexanoate or L can be

where R is as above e.g. alkyl, allenyl, amino or a fused ring such as acyclic or polycyclic ring.

The different groups Lm, Ln and Lp may also be

Large or complex molecular structures can be used in which a “cage” or“basket” structure is formed by the ligands Lm and Ln and Lp beingcondensed together and/or the metal atoms being linked by a hero atom oratoms such as oxygen, nitrogen etc.

For example the groups R, R₁, R₂ and R₃ on the ligands Lm and the groupsR, R₁, R₂ and R₃ on the ligands Ln can form a condensed or ringstructure e.g. substituted and unsubstituted fused aromatic,heterocyclic and polycyclic ring structures

Examples of such complexes are described in Chem. Abs. Vol 106 page 568,J. Chem Soc. Dalton Trans 1993 pps 2379 to 2386 and in Inorg. Chem.1994, 33, 1230-1233;

Optionally there can also be a neutral ligand Lq linked to the metal M₁and/or M₂

The groups Lq can be selected from

Where each Ph which can be the same or different and can be a phenyl(OPNP) or a substituted phenyl group, other substituted or unsubstitutedaromatic group, a substituted or unsubstituted heterocyclic or polyclicgroup, a substituted or unsubstituted fused aromatic group such as anaphthyl, anthracene, phenanthrene, prylene or pyrene group. Thesubstituents can be an alkyl, aralkyl, alkoxy, aromatic, heterocyclic,polyclic group, and halogen such as fluorine. Examples are given inFIGS. 1 and 2 of the drawings where R, R₁, R₂, R₄ and R₅ can be the sameor different and are selected from hydrogen, hydrocarbyl groups,substituted and unsubstituted aromatic, heterocyclic and polycyclic ringstructures, fluorocarbons such as trifluoryl methyl groups, halogenssuch as fluorine or thiophenyl groups; R, R₁, R₂, R₄ and R₅ can also becopolymerisable with a monomer e.g. styrene. R, R₁, R₂, R₃ and R₄ canalso be unsaturated alkylene groups such as vinyl groups or groups—C—CH₂═CH₂—Rwhere R is as above.

Lq can also be compounds of formulae

where R₁, R₂ and R₃ are as referred to above, for example bathophenshown in FIG. 3 of the drawings.

Lq can also be

where Ph is as above.

Other examples of Lq chelates are as shown in FIGS. 4 a to 4 l andfluorene and fluorine derivatives e.g., as shown in FIGS. 5 a to 5 f andcompounds of formulae as shown as shown in FIGS. 6 a to 6 e, 7 a to 7 fand 8 a to 8 h.

Specific examples of Lq are tripyridyl and TMBD, and TMHD complexes, α,α′, α″ tripyridyl, crown ethers, cyclans, cryptans phthalocyanans,porphoryins ethylene diamine tetramine (EDTA), DCTA, DTPA and TTHA.Where TMHD is 2,2,6,6-tetramethyl-3,5-heptanedionato and OPNP isdiphenylphosphonimide triphenyl phosphorane.

Preferred complexes of the present invention are shown in FIGS. 18, 19and 20 of the drawings where L₃ are the ligands Lm, Ln or Lp.

The first electrode is preferably a transparent substrate which is aconductive glass or plastic material which acts as the anode, preferredsubstrates are conductive glasses such as indium tin oxide coated glass,but any glass which is conductive or has a conductive layer can be used.Conductive polymers and conductive polymer coated glass or plasticsmaterials can also be used as the substrate.

Preferably there is a layer of a hole transporting material between thefirst electrode and the layer of the electroluminescent material.

The hole transporting material can be an amine complex such as poly(vinylcarbazole), N,N′-diphenyl-N,N′-bis (3-methylphenyl)-1,1′-biphenyl4,4′-diamine (TPD), an unsubstituted or substituted polymer of an aminosubstituted aromatic compound, a polyaniline, substituted polyanilines,polythiophenes, substituted polythiophenes, polysilanes etc. Examples ofpolyanilines are polymers of

where R is in the ortho—or meta-position and is hydrogen, C1-18 alkyl,C1-6 alkoxy, amino, chloro, bromo, hydroxy or the group

where R is alky or aryl and R′ is hydrogen, C1-6 alkyl or aryl with atleast one other monomer of formula I above.

Or the hole transporting material can be a polyaniline, polyanilineswhich can be used in the present invention have the general formula

where p is from 1 to 10 and n is from 1 to 20, R is as defined above andX is an anion, preferably selected from Cl Br, SO₄, BF₄, PF₆, H₂PO₃,H₂PO₄, arylsulphonate, arenedicarboxylate, polystyrenesulphonate,polyacrylate alkysulphonate, vinylsulphonate, vinylbenzene sulphonate,cellulose sulphonate, camphor sulphonates, cellulose sulphate or aperfluorinated polyanion.

Examples of arylsulphonates are p-toluenesulphonate, benzesulphonate,9,10-anthraquinone-sulphonate and anthracenesulphorate, an example of anarenedicarboxylate is phthalate and an example of arenecarboxylate isbenzoate.

We have found that protonated polymers of the unsubstituted orsubstituted polymer of an amino substituted aromatic compound such as apolyaniline are difficult to evaporate or cannot be evaporated, howeverwe have surprisingly found that if the unsubstituted or substitutedpolymer of an amino substituted aromatic compound is deprotonated the itcan be easily evaporated i.e. the polymer is evaporable.

Preferably evaporable deprotonated polymers of unsubstituted orsubstituted polymer of an amino substituted aromatic compound are used.The de-protonated unsubstituted or substituted polymer of an aminosubstituted aromatic compound can be formed by deprotonating the polymerby treatment with an alkali such as ammonium hydroxide or an alkalimetal hydroxide such as sodium hydroxide or potassium hydroxide.

The degree of protonation can be controlled by forming a protonatedpolyaniline and de-protonating. Methods of preparing polyanilines aredescribed in the article by A. G. MacDiarmid and A. F. Epstein, FaradayDiscussions, Chem Soc. 88 P319 1989.

The conductivity of the polyaniline is dependant on the degree ofprotonation with the maximum conductivity being when the degree ofprotonation is between 40 and 60% e.g. about 50% for example.

Preferably the polymer is substantially fully deprotonated

A polyaniline can be formed of octamer units i.e. p is four e.g.

This is referred to as DDPANI

The polyanilines can have conductivities of the order of 1×10⁻¹ Siemencm⁻¹ or higher.

The aromatic rings can be unsubstituted or substituted e.g. by a C1 to20 alkyl group such as ethyl.

The polyaniline can be a copolymer of aniline and preferred copolymersare the copolymers of aniline with o-anisidine, m-sulphanilic acid oro-aminophenol, or o-toluidine with o-aminophenol, o-ethylaniline,o-phenylene diamine or with amino anthracenes.

Other polymers of an amino substituted aromatic compound which can beused include substituted or unsubstituted polyaminonapthalenes,polyaminoanthracenes, polyaminophenanthrenes, etc. and polymers of anyother condensed polyaromatic compound. Polyaminoantacenes and methods ofmake them are disclosed in U.S. Pat. No. 6,153,726. The aromatic ringscan be unsubstituted or substituted e.g. by a group R as defined above,

Other hole transporting materials are conjugated polymer and theconjugated polymers which can be used can be any of the conjugatedpolymers disclosed or referred to in U.S. Pat. No. 5,807,627,PCT/WO90/13148 and PCT/WO92/03490.

The preferred conjugated polymers are poly (p-phenylenevinylene)-PPV andcopolymers including PPV. Other preferred polymers are poly(2,5dialkoxyphenylene vinylene) such as poly(2-methoxy-5-2-methoxypentyloxy-1,4-phenylene vinylene),poly(2-methoxypentyloxy)-1,4-phenylenevinylene),poly(2-methoxy-5-(2-dodecyloxy-1,4-phenylenevinylene) and other poly(2,5dialkoxyphenylenevinylenes) with at least one of the alkoxy groups beinga long chain solubilising alkoxy group, poly fluorenes andoligofluorenes, polyphenylenes and oligophenylenes, polyanthracenes andoligo anthracenes, ploythiophenes and oligothiophenes.

In PPV the phenylene ring may optionally carry one or more substituentse.g. each independently selected from allyl, preferably methyl, alkoxy,preferably methoxy or ethoxy.

Any poly(arylenevinylene) including substituted derivatives thereof canbe used and the phenylene ring in poly(p-phenylenevinylene) may bereplaced by a fused ring system such as anthracene or naphthlyene ringand the number of vinylene groups in each polyphenylenevinylene moietycan be increased e.g. up to 7 or higher.

The conjugated polymers can be made by the methods disclosed in U.S.Pat. No. 5,807,627, PCT/WO90/13148 and PCT/WO92/03490.

The thickness of the hole transporting layer is preferably 20 nm to 200nm.

The polymers of an amino substituted aromatic compound such aspolyanilines referred to above can also be used as buffer layers with orin conjunction with other hole transporting materials.

The structural formulae of some other hole transporting materials areshown in FIGS. 11, 12 and 13 to 16 of the drawings, where R₁, R₂ and R₃can be the same or different and are selected from hydrogen, andsubstituted and unsubstituted hydrocarbyl groups such as substituted andunsubstituted aliphatic groups, substituted and unsubstituted aromatic,heterocyclic and polycyclic ring structures, fluorocarbons such astrifluoryl methyl groups, halogens such as fluorine or thiophenylgroups; R₁, R₂ and R₃ can also form substituted and unsubstituted fusedaromatic, heterocyclic and polycyclic ring structures and can becopolymerisable with a monomer e.g. styrene. X is Se, S or O, Y can behydrogen, substituted or unsubstituted hydrocarbyl groups, such assubstituted and unsubstituted aromatic, heterocyclic and polycyclic ringstructures, fluorine, fluorocarbons such as trifluoryl methyl groups,halogens such as fluorine or thiophenyl groups or nitrile.

Examples of R₁ and/or R₂ and/or R₃ include aliphatic, aromatic andheterocyclic alkoxy, aryloxy and caboxy groups, substituted andsubstituted phenyl fluorophenyl, biphenyl, phenanthrene, anthracene,naphthyl and fluorene groups alkyl groups such as t-butyl, heterocyclicgroups such as carbazole.

Optionally there is a layer of an electron transmitting material betweenthe cathode and the electroluminescent material layer, the electrontransmitting material is a material which will transport electrons whenan electric current is passed through electron transmitting materialsinclude a metal complex such as a metal quinolate e.g. an aluminiumquinolate, lithium quinolate a cyano anthracene such as 9,10 dicyanoanthracene, a polystyrene sulphonate and compounds of formulae shown inFIGS. 9 and 10. Instead of being a separate layer the electrontransmitting material can be mixed with the electroluminescent materialand co-deposited with it.

In general the thickness of the layers is from 5 nm to 500 nm.

The second electrode functions as the cathode and can be any low workfunction metal e.g. aluminium, calcium, lithium, silver/magnesium alloysetc., aluminium is a preferred metal. Lithium fluoride can be used asthe second electrode for example by having a lithium fluoride layerformed on a metal.

The hole transporting material can optionally be mixed with theelectroluminescent material in a ratio of 5-95% of theelectroluminescent material to 95 to 5% of the hole transportingcompound.

The hole transporting materials, the electroluminescent material and theelectron injecting materials can be mixed together to form one layer,which simplifies the construction.

The electroluminescent material can be deposited on the substratedirectly by evaporation from a solution of the material in an organicsolvent. The solvent which is used will depend on the material butchlorinated hydrocarbons such as dichloromethane, n-methylpyrrolidone,dimethyl sulphoxide, tetra hydrofuran dimethylformamide etc. aresuitable in many cases.

Alternatively the material can be deposited by spin coating fromsolution or by vacuum deposition from the solid state e.g. by sputteringor any other conventional method can be used.

The invention is illustrated in the following examples in which Examples1 to 9 show the synthesis of the ligands

EXAMPLE 1 Methylene-bis(diphenylphospbane oxide)

To a solution of Bis(diphenylphospbino)methane (2.0 g, 5.2 mmol,Sigma-Aldrich) in 50 mL ethanol was added 2 drops of 0.5M sodiumhydroxide solution. Hydrogen peroxide (2.4 mL 30% wt solution, 21.0mmol. BDH) was introduced dropwise over 1 minute, the reaction cooled to5° C. and stored for 3 hours. Heating to 60° C. afforded completedissolution of the white precipitate. Addition of deionised water untilthe cloud-point, followed by storage at 5° C. for 12 hours yielded 2.0 g(92%) of the desired product (colourless crystals), mp. 182-3° C.

Anal. Cald. for C₂₅H₂₂O₂P₂: C, 72.11; H, 5.33.

EXAMPLE 2 Ethylene-1,2-bis(diphenylphosphane oxide)

To a solution of 1,2-Bis(diphenylphosphino)ethane (2.0 g. 5.0 mmol,Sigma-Aldich) in 50 mL ethanol was added 2 drops of 0.5M sodiumhydroxide solution. Hydrogen peroxide (2.3 mL 30% wt solution, 20.0mmol, BDH) was introduced dropwise over 1 minute, the reaction cooled to5° C. and stored for 3 hours. Heating to 60° C. afforded completedissolution of the white precipitate. Addition of deionised water untilthe cloud-point, followed by storage at 5° C. for 12 hours yielded 1.95g (90%) of the desired product (colourless crystals), mp. 271-3° C.

Anal. Cald. for C₂₆H₂₄O₂P₂: C, 72.55; H, 5.62; P, 14.39.

EXAMPLE 3 Butylene-1,4-bis(diphenylphospane oxide)

To a solution of 1,4-Bis(diphenylphosphino)butane (2.0 g. 4.7 mmol,Sigma-Aldrich) in 50 mL ethanol was added 2 drops of 0.5M sodiumhydroxide solution. Hydrogen peroxide (2.3 mL 30% wt solution, 20.0mmol, BDH) was introduced dropwise over 1 minute, the reaction cooled to5° C. and stored for 3 hours. Heating to 60° C. afforded completedissolution of the white precipitate. Addition of deionised water untilthe cloud-point, followed by storage at 5° C. for 12 hours yielded 1.80g (84%) of the desired product (colourless crystals), m.p. 145° C.

Anal. Cald. for C₂₈H₂₈O₂P₂: C, 73.35; H. 6.16

EXAMPLE 4 Ethylene-1,4-bis(dipyridylphosphane oxide)

To a solution of 1,2-Bis(dipyridylphosphino)ethane (0.5 g, 1.24 mmol) in50 mL ethanol was added 2 drops of 0.5M sodium hydroxide solution.Hydrogen peroxide (0.5 mL 30% wt solution, 5 mmol, BDH) was introduceddropwise over 1 minute, the reaction cooled to 5° C. and stored for 3hours. Heating to 60° C. afforded complete dissolution of the whiteprecipitate. The product (0.5 g. 93%) was recrystallised frommethanol/water.

Anal. Cald. for C₂₂H₂₀N₄O₂P₂:C, 60.83; H4.64; N, 12.80

EXAMPLE 5 Bis(2-diphenylphosphane oxide-ethyl)phenylphosphane oxide

To a solution of Bis(2-diphenylphosphinoethyl)phenylphosphane (2.0 g.3.74 mmol, Sigma-Aldrich) in 80 mL ethanol was added 2 drops of 0.5Msodium hydroxide solution. Hydrogen peroxide (2.5 mL 30% wt solution,22.0 mmol, BDH) was introduced dropwise over 1 minute, the reactioncooled to 5° C. and stored for 3 hours. Heating to 60° C. affordedcomplete dissolution of the white precipitate. Addition of deionisedwater until the cloud-point, followed by storage at 5° C. for 12 hoursyielded 1.90 g (90%) of the desired product (colourless crystals), mp.304-5° C.

Anal. Cd. for C₃₄H₃₃O₃P₃: C, 70.10; H, 5.71.

EXAMPLE 6 Methylene-bis(diphenylphosphinimino-phosphane oxide)

Diethylether (50 mL, dried and distilled over sodium) was added toBis(diphenylphosphino)methane (2.0 g. 5.2 mmol, Sigma-Aldrich in athree-necked flask equipped with condenser, pressure-equalising droppingfunel and under a nitrogen atmosphere. Diphenylazidophosphane (2.78 g,11.0 mmol) in dry diethylether (100 mL) was added dropwise over 15minutes to the suspension. A further 50 mL diethylether was used torinse the pressure-equalising dropping funnel, which was subsequentlyremoved and the reaction refluxed for 3 hours. After stirring for 15hours at room temperature, a white precipitate (3.0 g. 71%) was filteredand washed with diethylether. Recrystallisation from toluene/hexaneyielded an analytically pure sample, m.p. 208-9° C. Anal. Cald. forC₄₉H₄₂N₂O₂P₄: C, 72.23; H, 5.20; N, 3.44.

EXAMPLE 7 Ethylene-1,2-bis(diphenylphosphinimino-phosphane oxide)

Diethylether (50 mL, dried and distilled over sodium) was added to1,2-Bis(diphenylphosphinoethane (4.0 g, 10.0 mmol, Sigma-Aldrich) in athree-necked flask equipped with condenser, pressure-equalising droppingfunnel and under a nitrogen atmosphere. Diphenylazidophosphane (6.0 g.25.0 mmol) in dry diethylether (100 mL) was added dropwise over 15minutes to the suspension. A further 50 mL diethylether was used torinse the pressure-equalising dropping funnel, which was subsequentlyremoved and the reaction refluxed for 3 hours. After stirring for 15hours at room temperature, a white precipitate (7.95 g, 96%) wasfiltered and washed with diethylether. Recrystallisation fromethanol/water yielded an analytically pure sample, m.p. 230° C. Anal.Cald. for C₅₀H₄₄N₂O₂P₄: C, 72.46; H, 5.35; N, 3.38; P, 14.95.

EXAMPLE 8 Butylene-1,4-bis(diphenylphosphinimo-phosphane oxide)

Diethylether (50 mL, dried and distilled over sodium) was added to1,4-Bis(diphenylphosphino)butane (2.5 g 5.86 mmol, Sigma-Aldrich) in athree-necked flask equipped with condenser, pressure-equalising droppingfunnel and under a nitrogen atmosphere. Diphenylazidophosphane (2.71 g.11.2 mmol) in dry diethylether (50 mL) was added dropwise over 15minutes to the suspension. A further 50 mL diethylether was used torinse the pressure-equalising dropping funnel, which was subsequentlyremoved and the reaction refluxed for 3 hours. After stirring for 15hours at room temperature, a white precipitate (4.27 g, 85%) wasfiltered and washed with diethylether. Recrystallisation fromtoluene/hexane yielded an analytically pure sample, m.p. 206-7° C. Anal.Cald. for C₅₂H₄₈N₂O₂P₄: C, 72.89; H, 5.65; N, 3.27.

EXAMPLE 9 Hexylene-1,6-bis(diphenylphosphinimino-phosphane oxide)

Diethylether (50 mL, dried and distilled over sodium) was added to1,6-Bis(diphenylphosphino)hexane (2.5 g, 5.5 mmol. Sigma-Aldrich) in athree-necked flask equipped with condenser, pressure-equalising droppingfunnel and under a nitrogen atmosphere. Diphenylazidophosphane (2.56 g,10.Smmol) in dry diethylether (50 mL) was added dropwise over 15 minutesto the suspension. A further 50 mL diethylether was used to rinse thepressure-equalising dropping funnel, which was subsequently removed andthe reaction refluxed for 3 hours. After stirring for 15 hours at roomtemperature, a white precipitate (3.3 g, 68%) was filtered and washedwith diethylether. Recrystallisalion from toluene/hexane yielded ananalytically pure sample, m.p. 245° C. Anal. Cald. for C₅₄H₅₂N₂O₂P₄: C,73.29; H. 5.92; N, 3.16.

EXAMPLE 10 Methylene-bis(diphenylphosphane oxide)bis-[terbiumtri(tetramethylheptanedione)

1.18 g (2.83 mmol) of Methylene-bis(diphenylphosphane oxide) and 4.0 g(5.66 mmol)

Terbium tris(tetramethylheptanedione) were dissolved in 80 mLchloroform. The solution was heated for 1 hour and the solvent removedunder vacuum to yield an oily residue. Addition of acetonitrile gave awhite precipitate (4.0 g. 77%), which was filtered, washed with furtheracetonitrile and dried under vacuum at 80° C., mp. 195° C.

Anal. Cald. for C₉₁H₁₃₆O₁₄P₂Tb₂:C, 59.60; H, 7.48;P,3.38.

Photoluminescence: PL_(:eff.) :0.28 cd m⁻² μmW⁻¹ @630 μW; peak=548 nmCIE coordinates x: 0.32, y: 0.61.

EXAMPLE 11 Butylene-bis(diphenylphosphane oxide)bis[terbiumtris(tetramethylheptanedione)]

0.50 g (1.09 mmol) of Butylene-bis(diphenylphosphane oxide) and 1.55 g(2.18 mmol) Terbium tris(tetramethylheptanedione) were dissolved in 80mL chloroform. The solution was heated for 1 hour and the solventremoved under vacuum to yield an oily residue. Addition of acetonitrilegave a white precipitate (3.0 g, 94%), which was filtered, washed withfurther acetonitrile and dried under vacuum at 80° C., m.p. 212° C.Anal. Cald. for C₉₄H₁₄₂O₁₄P₂Tb₂: C, 60.18; H 7.63; Tn, 16.04.

Photoluminescence:

PL_(:eff.) :0.25 cd m⁻² μmW⁻¹ @870 μW; peak=545 nm CIE coordinates x:0.31, y: 0.62. (Terbium tris(tetramethylheptanedione) was prepared fromTetramethylheptanedione, Terbium (III) chloride and Ammonium hydroxide.It is also available commercially.)

EXAMPLE 12 Butylene-bis(diphenylphosphane oxide)bis[europiumtris(dibenzoylmethane)]

0.50 g (1.09 mmol) of Butylene-bis(diphenylphosphane oxide) and 1.79 g(2.18 mmol) Europium tris(dibenzoymethane) were dissolved in 80 mLchloroform The solution was heated for 1 hour and the solvent reducedunder vacuum to approximately 2 mL. Petroleum ether (40-60° C.) wasadded until the cloud point, the reaction cooled to 5° C. and storeduntil a yellow precipitate had formed. This was filtered (2.1 g, 92%),washed with petroleum ether (40-60° C.) and dried under vacuum at 80°C., mp. 212° C.

Anal. Cald. for C₁₁₈H₉₄O₁₄P₂Eu₂:C, 67.43; H, 4.51Photolumimscence:PL_(:eff.) :0.12 cd m⁻² μmW⁻¹ @800 μW; peak=613 nm CIEcoordinates x: 0.66, y: 0.33.

EXAMPLE 4 Ethylene-bis(dipyridylphosphane oxide)-bis[terbiumtris(tetramethylheptanedione)]

0.34 g (0.78 mmol) of Ethylene-bis(diphenylphosphane oxide) and 1.1 ig(1.57 mmol) Terbium tris(tetramethylheptanedione) were dissolved in 60mL chloroform The solution was heated for 1 hour and the solvent removedunder vacuum to yield an oily residue. Acetonitrile was added and thewhite precipitate was filtered and washed with further acetonitrile.This was recrystallised from toluene/hexane and dried under vacuum at80° C. to give an analytically pure sample (1.2 g, 83%), m.p. 240-241.5°C.

Anal. Cald. for C₈₈H₁₃₄N₄O₁₄P₂Tb₂: C, 57.08; C, 56.97.Photoluminescence:PL_(:eff.) :0.26 cd m⁻² μmW⁻¹ @880 μW; peak=548 nm CIEcoordinates x: 0.31, y: 0.62.

EXAMPLE 13

1.0 g (1.72 mmol) of Bis(2-diphenylphosphane oxide-ethyl)phenylphosphaneoxide was dissolved dissolved in 80 mL chloroform 3.65 g (5.15 mmol)Terbium tris(tetramethylheptanedione) was dissolved in 120 miLacetonitrile. The two solutions were mixed at 60° C. and heated for 1hour. The solvent reduced under vacuum to yield an oily residue.Acetonitrile was added to afford a white precipitate (3.9 g. 84%), whichwas collected and washed with further acetonitrile. An analytical samplewas recrystallised from toluene/hexane and dried under vacuum at 80° C.,nip. 202-6° C.

Anal Cald. for C₉₄H₁₄₂O₁₄P₂Tb₂: C, 60.18; H, 7.63; Th 16.95.Photoluminescence: PL_(:eff.) :0.27cd m⁻² μmW⁻¹ @880 μW; peak=548 mm CIEcoordinates x: 0.31, y: 0.62.

EXAMPLE 14 Methylene-bis(diphenylphosphinimino-phosphaneoxide)-bis˜terbium tris(tetramethytheptanedione)]

0.57 g (0.71 mmol) of Methylene-bis(diphenylphosphinimino-phosphaneoxide) and 1.0 g (1.41 mmol) Terbium tris(tehramethylheptanedione) weredissolved in 80 mL chloroform. The solution was heated for 1 hour andthe solvent removed under vacuum to yield an oily residue. Addition ofacetonitrile gave a white precipitate (1.4 g. 89%), which was filtered,washed with further acetonitrile and dried under vacuum at 80° C., m.p.275-7° C.

Anal. Cald. for C₁₁₅H₁₅₆N₂O₁₄P₄Tb₂: C, 61.88; H, 7.04; N, 1.25; P, 5.55;Tb, 14.94. Photoluminescence: PL_(:eff.) :0.28 cd m⁻² μmW⁻¹ @630 μW;peak=548 nm CIE coordinates x: 0.32, y: 0.61.

EXAMPLE 15 Ethylene-bis(diphenylphosphinimino-phosphaneoxide)bis[terbium tris(tetramethylheptanedione)]

0.585 g (0.71 mmol) of Ethylene-bis(diphenylphosphinimino-phosphaneoxide) and 1.0 g (1.41 mmol) Terbium tris(tetramethylheptanedione) weredissolved in 100 mL chloroform. The solution was heated for 1 hour andthe solvent removed under vacuum to yield an oily residue. Addition ofacetonitrile gave a white precipitate (1.4 g 88%), which was filtered,washed with further acetonitrile and dried under vacuum at 80° C., mp.240-2° C.

Anal. Cald for for C₁₁₆H₁₅₈N₂O₁₄P₄Tb₂:C, 62.03; H, 7.09; N, 1.25; P,5.52; Tb, 14.15. Photoluminescence: PL_(:eff.) :0.23 cd m⁻² μmW⁻¹ @630μW; peak=547 nm CIE coordinates x: 0.31, y 0.62.

EXAMPLE 16 Ethylene-bis(diphenylphosphinimino-phosphaneoxide)-bis˜europium tris(dibenzoyhnethane)]

1.01 g (1.22 mmol) of Ethylene-bis(diphenylphosphinimino-phosphaneoxide) and 2.0 g (2.43 mmol) Europium tris(dibenzoyhnethane) weredissolved in 50 mL dichloromethane. The solution was heated for 1 hourand the solvent removed under vacuum to yield an oily residue.Recrystallisation from toluene/petroleum ether (40-60° C.) affordedyellow/orange crystals (2.5 g, 83%), which were filtered, washed withfurther petroleum ether (40-60° C.) and dried under vacuum at 80° C.,m.p. 236-8° C.

Anal for C₁₄₀H₁₁₀N₂O₁₄P₄Eu₂ C, 68.02; H. 4.48; N, 1.13; P, 5.01; Eu,12.29. Photoluminescence: PL_(:eff.) :0.0.08 cd m⁻² μmW⁻¹ @820 μW;peak=612 nm CIE coordinates x: 0.66, y: 0.33.

EXAMPLE 17 Butylene-bis(diphenylphosphinimino-phosphaneoxide)-bis˜terbium tris(tetramethylheptanedione)]

0.5 g (0.58 mmol) of Butylene-bis(diphenylphosphinimino-phosphane oxide)and 0.83 g (1.17 mmol) Terbium tris(tetramethytheptanedione) weredissolved in 80 mL chloroform. The solution was heated for 1 hour andthe solvent removed under vacuum to yield an oily residue. Addition ofacetonitrile gave a white precipitate (0.8 g. 60%), which was filtered,washed with further acetonitrile and dried under vacuum at 80° C., m.p.248-250° C.

Anal Cald. for C₁₁₈H₁₆₂N₂O₁₄P₄Tb₂ C, 62.32; H, 7.18; N, 1.23; P, 5.45;Tb, 13.98.

EXAMPLE 18 Butylenebis(diphenylphosphinimno-phosphaneoxide)-bis{europiumtris˜4,4,4-trifluoro-1-(2-naphthyl)-1,3˜butanedione}}

0.53 g (0.62 mmol) of Butylene-bis(diphenylphosphinimino-phosphaneoxide) and 1.1 7 g (1.24 mmol) Europiumtris˜4,4,4-trifuoro-1-(2-naphthyl)-1,3-butanedione] were dissolved in100 mL dichloromethane. The solution was heated for 1 hour and thesolvent reduced to approximately 2 mL. Petroleum ether (40-60° C.) wasadded until the cloud point Storage at 5° C. for 3 hours yielded ayellow precipitate (1.0 g, 59%). This was filtered, washed with furtherpetroleum ether (40-60° C.) and dried under vacuum at 80° C., m.p. 184°C. (T_(g)-82° C.).

Anal. Cald. for C₁₃₆H₉₆N₂O₁₄F₁₅P₄Eu₂:C, 59.36; H, 3.52; N, 1.02.Photoluminescence: PL_(:eff.) :0.0.08 cd m⁻² μmW⁻¹ @820 μW; peak=612 nmCIE coordinates x: 0.66, y: 0.33. (Europiumtris˜4,4,4-trifluoro-I-(2-naphthyl)-I,3-butanedione] was synthesisedfrom Europium (III) chloride,4,4,4-Trifluoro-1-(2-naphthyl)-1,3-butanedione (Fluorochem) and Ammoniumhydroxide.)

EXAMPLE 19 Electroluminescent Device

An electroluminescent device was made by depositing sequentially fromsolution onto a indium tin oxide glass anode layers of DDPANI 8 nm;α-NPB; an electroluminescent layer comprising a compound made as inExample 14; aluminium quinolate and an aluminium cathode. The device isshown schematically in FIG. 21 where (1) is the ITO anode; (2) is aDDPANI layer; (3) is an α-NPB layer, (4) is the electroluminescent layercomprising a compound made as in Example 14; (5) is an aluminiumquinolate layer and (6) is an aluminium cathode.

An electric current was passed between the aluminium cathode and ITOanode and the device emitted a green light with a peak wavelengthλ_(max) of 546 nm. The properties were measured and the results shown inFIGS. 22 and 23. Another device was made replacing theelectroluminescent layer with a compound of formula as in Example 16,the device emitted a red length with a peak wavelength λ_(max) of 611nm.

1. An electroluminescent device comprising a first electrode, a secondelectrode, and a layer comprising an electroluminescent compound betweenthe first electrode and the second electrode wherein: theelectroluminescent compound is selected from the group consisting ofbinuclear, trinuclear and polynuclear metal complexes in which nucleiare defined by at least two metal atoms, at least one of said metalatoms being selected from the group consisting of Sm (III), Eu (II), Eu(III), Tb (III), Dy(III), Yb (III), Lu (III), Gd (III), U(III), Tm(III), Ce (III), Pr (III), Nd (III), Pm (III), Dy (III), Ho (III), Er(III), and Yb (III), and at least a second of said metal atoms isselected from the group consisting of lithium, sodium, potassium,rubidium, cesium, beryllium, magnesium, calcium, strontium, barium,boron, aluminum, gallium, indium, germanium, tin, antimony, lead andmetals of the first, second and third groups of transition metals;further wherein each metal atom is linked to another metal atom througha bridging ligand, said bridging ligands each having the generalchemical formula:

wherein: the groups R can be the same or different and are independentlyselected from the group consisting of hydrogen, substituted andunsubstituted aliphatic groups, substituted and unsubstituted aromatic,heterocyclic and polycyclic ring structures, fluorocarbon groups andhalogen atoms; Ar represents a substituted or unsubstituted aromatic orheteroaromatic group; and further wherein n is an integer from 1 to 10.2. The device of claim 1, wherein said at least one of said metal atomsis selected from the group consisting of Eu (III), Tb (III), Dy (III),and Gd(III).
 3. The device of claim 1, further comprising a layer of ahole transmitting material located between an electrode that serves asan anode and the electroluminescent layer.
 4. The device of claim 3,wherein the hole transmitting material is a film of a polymerizedaromatic amine.
 5. The device of claim 3, wherein the hole transmittingmaterial is a film comprising a material selected from the groupconsisting of poly (vinylcarbazole),N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD);polyaniline; substituted polyanilines; polythiophenes; substitutedpolythiophenes; polysilanes; and substituted polysilanes.
 6. The deviceof claim 3, wherein the hole transmitting material is an aromatic amineselected from the group consisting of the following compounds:


7. The device of claim 1, further comprising a layer of an electrontransmitting material located between an electrode that serves as acathode and the electroluminescent material layer.
 8. The device ofclaim 7, wherein the electron transmitting material is a metalquinolate.
 9. The device of claim 8, wherein the metal quinolate isaluminium quinolate or lithium quinolate.
 10. The device of claim 9,wherein the electrode that serves as a cathode comprises a materialselected from aluminium, calcium, lithium, and silver/magnesium alloys.11. The device of claim 10, wherein a lithium fluoride layer is formedon the electrode that serves as a cathode, said lithium fluoride layerbeing located between the cathode and the electron transmittingmaterial.
 12. The device of claim 1, wherein each bridging ligand isselected from the group consisting of one of the following chemicalformulas in which Ar represents a substituted or unsubstituted aromaticor heteromatic group: